This proposal is for renewal of our postdoctoral research training grant in Immunohematology and Transfusion Medicine that was initiated in 2001. The program provides a highly organized 2-3 year program of focused dedicated didactics, seminars, and, most importantly, an intense research experience with one of 24 well-established, highly interactive, and well-funded cross-disciplinary mentors representing eight different primary departments. The goal is to generate productive MD and MD/PhD physician- scientists as well as PhD scientists and clinician-scientists, who will be launched on a lifelong investigative career pursuing basic and translational research in this underrepresented field. Careful career development by an individualized Career & Research Committee is a hallmark of the program. Three degree-granting tracks are also available, in addition to the core post-doctoral program: an Investigative Medicine PhD available to MD-only trainees who wish to obtain a more expansive research background mimicking that of an MD/PhD; a Masters of Health Sciences under the aegis of the Yale CTSA for those with a clinical/translational research goal; and a Masters of Biomedical Engineering for trainees with a past basic biomedicine emphasis who wish to add an engineering dimension to their knowledge base. Drawn from a candidate pool focused on those whose background is Laboratory Medicine & Pathology (a pool which has always included at least 10 fold more excellent candidates than are accepted into the program), outcomes have been quite positive. Of the graduates of the T32 program, 25% have successfully completed a degree-granting track, 50% have secured tenure track academic investigative positions, with the remainder retained in research at earlier career development stages; all have obtained some subsequent funding with 25% moving directly to K08 awards. The T32 program currently supports four post-doctoral positions per year and, based on results and candidate pool, we are requesting an increase to six positions. The core T32 is leveraged, since the entire Laboratory Medicine Departmental Immunohematology-Transfusion Medicine training program is greater than the T32 - it includes individuals on other funding mechanisms. When they are included, 69% of graduates have investigative tenure track positions and 38% have attained PI-level R01 funding. We believe that this program fills an important research training need both at Yale and nationally.